> (For the astronauts, speeding into space at one and a half times the speed of sound, a mile and a half up, time, according to Einstein, was literally slowing

> (For the astronauts, speeding into space at one and a half times the speed of sound, a mile and a half up, time, according to Einstein, was literally slowing down.) Indeed! Those intrepid relativistic explorers, at Mach 1.5, would experience 0.99999999999855 seconds for every 1 we poor earth-bound non-moving folks did. Of course, once they were on the way to the moon, moving at the far faster 11 km/s, then they'd really start to get some relativity going on: 0.9999999993 seconds for every 1 in our rest frame.